Magnesium base alloy



Patented July 26, 1938 PATENT OFFICE MAGNESIUM BASE ALLOY John A. Gann, Midland, Mich., assignor to The Dow Chemical Company, Midland, Mich, a corporation of Michigan No Drawing. Original application August 2, 1937,

Serial No. 156,942. Divided and this application February 3, 1938, Serial No. 188,459

4 Claims.

The present invention relates to magnesium alloys and more particularly to those in which magnesium is the predominant constituent.

Most of the present commercial uses for magnesium alloys are due to their high strength and high strength-weight ratio. If these characterlstics could be further improved, the field of application of these light weight alloys would be greatly extended.

The principal object of this invention is to produce magnesium alloys having improved physical properties. A more specific object is to produce magnesium alloys that are amenable to heat treatment. Other objects and advantages will appear as the description proceeds.

This invention is based on the discovery that the properties of magnesium-aluminu'm-cadmium-manganese alloys as described in United States Patent No. 1,959,913 may be improved to a very marked extent by the addition of relatively small amounts of zinc, without appreciably in creasing the specific gravity of the alloy. I have discovered that maximum property improvement is obtained when these alloys are subjected to the well known methods of solution heat treatment and solution heat treatment plus aging. I have also found that the advantages occurring from the addition of zinc are present when approximately 0.5 to 8 percent of zinc are added to magnesium alloys containing from about 1 to 12 per cent of aluminum, from about 0.5 to 10 per cent of cadmium, and from about 0.1 to 0.5 per cent of manganese.

Specific examples of the property improvements that result in the production of my new alloy by adding zinc to the well known magnesium-aluminum-cadmium-manganese alloys are shown in the following tables where illustrations are given of cast, solution heat treated, and solution heat treated and aged alloys.

Solution heat treated alloys Nominal composition in percent (Mg=remainder) Tensile Yield ifif l fi f i sq. in. sq. 11. Al Cd Mn f Zn Solution heat healed and aged alloys I have likewise discovered that the addition of zinc to magnesium-aluminum-cadmium-manganese alloys has resulted in a marked improvement in' corrosion resistance. This beneficial eflect of zinc is particularly pronounced in the case of the cast and the solution heat treated and aged alloys, although it is evident in some of the solution heat treated alloys. The following table illustrates this improvement as obtained from alternate immersion tests conducted for one week in a 3 per cent salt solution.

N omlnal composition in Loss in weight mg/cm'lday percen (Mg=remainder) Al 0d Mn Zn Cast 8. H. T. B. P. H. TJ

1 S. H. T.=Bolutiou heat treated. S. P. H. T.-Bolution heat treated and aged.

I have furthermore discovered that ii. my improved alloy likewise contains approximately 0.5 to 10 percent of lead, or, in other words, if the improved alloy is obtained by adding both lead and zinc to the magnesium-aluminum-cadmiummanganese alloy, that the resultant composition is superior to that obtained when only one of the metals, lead or zinc, is added to the known magnesium-aluminum-cadmium-manganese alloy.

This is illustrated, for example, by the yield strength and hardness data in the following table:

' Nominalin composition W Yield (mzmmalnder) Condition 23 2 A] Cd Mn Pb Zn 8 2 0. 2 11, 5G) 46. 4 8 2 0. 2 i3, 800 50. 6 8 2 0. 2 14, H!) 56. 5 8 2 0. 2 l6, 2) 69. 2 7 2 0. 2 14, am 66. 5

8 2 0. 2 13, 200 51. 8 8 2 0. 2 16, (ll) 60. 2 8 2 0. 2 Z3, 200 76. 6 8 2 0. 2 24, 000 76. 6 7 2 0. 2 21, 400 72. 0

l S. H. 'I.=Solution heat treated.

I S. P. H. 'l.-Bolution heat treated and aged- When the alloy is to be used for the production of castings, I normally prefer to use compositions containing approximately to 92 per cent of magnesium, from 4 to 10 per cent of aluminum. from 1 to 6 per cent of cadmium, from 0.1 to 0.3 per cent of manganese, and from 2 to 6 per cent of zinc. Where lead is likewise required, it should be present in amounts ranging from about 1 to 6 per cent. When the alloy is to be used in plastic deformation operations it should, in general, contain to 96 per cent of magnesium, and the various alloying elements in the following proportions: 1 to 8 per cent of aluminum, 0.5 to 3 per cent of cadmium, 0.1 to 0.5 per cent of manganese, 0.5- to 2 percent of lead, and 0.5 to 2 per cent of zinc.

My new polynary alloys may be prepared by the methods usually employed for melting and alloying metals with magnesium, such as adding the respective alloying metals singly or jointly to a bath of molten magnesium protected from oxidation by a, cover of fluid flux. The solution heat.

treatment for the zinc-free alloys may consist in amuse heating the material for 20 hours at 430 (3., followed by air cooling, or, when zinc is present in the alloy, 12 hours at 320 0. plus 16 hours at 420 C., followed by air cooling. The aging treatment consists of approximately 16 hours heating at 0., subsequent to the above solution heat treatment. Plastic deformation operations, such as extruding, forging, and rolling are best conducted at temperatures between 300 and 400 C.

This application is a division of my co-pending application Serial No. 156,942, filed August 2, 1937.

Other modes oi applying the principle of my invention may be employed instead of those explained, change being made as regards the ingredients and the steps herein disclosed, provided those stated by any of the following claims or their equivalent be employed.

I particularly point out and distinctly claim as my invention:

1. A magnesium-base alloy containing from approximately 1 to '12 per cent of aluminum, and from about 0.5 to 10 per cent of cadmium, and from about 0.1 to 0.5 per cent of manganese, and from about 0.5 to 8 per cent of zinc, and from about 1 to 10 per cent of lead, the balance being magnesium.

2. A magnesium-base alloy consisting of approximately 4 to 10 per cent of aluminum, and from about 1 to 6 per cent of cadmium, and from about 0.1 to 0.3 per cent of manganese, and from about 2 to 6 per cent of zinc, and from about 1 to 6 per cent of lead, the balance being magnesium.

3. A magnesiumbase alloy consisting of approximately 1 to 8 per cent of aluminum, and from about 0.5 to 3 per cent of cadmium, and from about 0.1 to 0.5 per cent of manganese, and from about 0.5 to 2 per cent of lead, and from about 0.5 to 2 per cent of zinc, and from about 90 to 96 per cent of magnesium.

4. A magnesium-base alloy consisting of approximately 8 per cent of aluminum, and 2 per cent of cadmium, and 0.2 per cent of manganese, and 8 per cent of lead, and 2 per cent of zinc, the balance being magnesium.

JOHN A. GANN. 

